Yep, as you may have noticed, Free RPG Day was pushed back this year. Normally held in June, this year, due to the pandemic, it was moved to October.
ENWorld has a surprisingly complete overview of what is available. As usual, the OSR relevant or adjacent are minimal.
Tomb of the Savage Kings for Dungeon Crawl Classics (DCC RPG), a level 2 adventure designed by Stephen Newton.
Warhammer Age of Sigmar: Soulbound: Reap and Sow gives an introductory adventure for players interested in visiting the Mortal Realms in Soulbound. Great for Age of Sigmar fans.